1. Field of the Invention
This invention relates to pointing devices used as input devices for computers, and particularly pointing devices that are actuated or steered by the movement of a keyboard.
2. Description of the Related Art
Pointing devices that allow user input to programs operating on computers, for example for controlling cursor or pointer movement on the computer's display, are a common part of most computer systems. In particular, computer programs employing graphical user interfaces make extensive use of pointing devices to access program functions. A variety of different pointing devices are well known and include: pointing sticks, trackballs, touchpads, and mice.
Pointing sticks feature a small vertical beam projecting upward from the keyboard or some other portion of a computer system. Because they are relatively small devices, pointing sticks are often used in portable computer systems where space is at a premium. Pointing sticks may be deflected in any direction perpendicular to the vertical, the amount and direction of applied force determining the direction and the distance a pointer or cursor moves on the display of the computer system. Pointing sticks are accompanied by one or more pointing device pick buttons which are momentarily activated switches (i.e. switches having discrete on and off states depending on applied pressure) that a user may selectively depress, thereby sending commands to the computer system. However, many users find pointing sticks counterintuitive and difficult to use, in part because of their small size (typically comparable to that of a pencil eraser). Additionally, long-term use of pointing sticks leads some users to develop finger numbness or pain due to the excessive pushing forces applied to the vertical beam.
Trackballs typically include a base adapted to cradle a freely rotatable ball which, in turn, can be rotated by a user's palm or fingers. Rotation of the ball usually actuates a pair of rollers whose motion is translated into X-Y motion for purposes of pointer or cursor movement. Trackballs are accompanied by one or more pointing device pick buttons which are momentarily activated switches that a user may selectively depress, thereby sending commands to the computer system. Trackballs do suffer from several significant disadvantages. For example, the rollers usually used by trackballs accumulate debris, particularly because at least some portion of the trackball is exposed and because of constant contact with a users hand or fingers. Additionally, trackballs generally require a large volume to package, a particular disadvantage in portable computer systems where space and size are always at a premium.
Touchpads are characterized by a substantially immobile base having a touch-sensitive membrane sensor pad located on a top surface. When a user touches a portion of the sensor pad, the portion either mechanically compresses or registers a change in some electrical property (e.g. capacitance), thereby locating where the user has touched the touchpad. The location is translated into location information for cursor or pointer movement. Additionally, non-position related input can be made through a touchpad. For example, commands similar to those issued by activation of a pointing device pick button can be issued using a touch pad when a user touches the same location on the touch pad twice in succession. Like pointing sticks, many users find touchpads difficult to use and uncomfortable to use for prolonged periods. Additionally, touchpads consume large surface areas on computer systems, which is a feature particularly troublesome for portable computer systems.
A mouse is perhaps the most common pointing device used for computer systems, but it too suffers from significant disadvantages. A mouse requires a stable and sizable work surface for proper use and suffers from many of the same cleaning problems as trackballs because most mice use rollers similar to those in trackballs. A mouse is also disadvantageous when used with portable computer systems because it is not an integrated part of the system, and thus it must be disconnected form the portable computer system and carried separately when the portable computer system is transported.
Accordingly, it is desirable to have a pointing device that is: easily integrated into a computer system and particularly a portable computer system, intuitive to use, ergonomic in that it minimizes physical strain on the user, and relatively small, consuming minimal surface area and/or volume.